Environmental constraints upon locomotion and predator-prey interactions in aquatic organisms: an introduction

Environmental constraints in aquatic habitats have become topics of concern to both the scientific community and the public at large. In particular, coastal and freshwater habitats are subject to dramatic variability in various environmental factors, as a result of both natural and anthropogenic processes. The protection and sustainable management of all aquatic habitats requires greater understanding of how environmental constraints influence aquatic organisms. Locomotion and predator-prey interactions are intimately linked and fundamental to the survival of mobile aquatic organisms. This paper summarizes the main points from the review and research articles which comprise the theme issue 'Environmental constraints upon locomotion and predator-prey interactions in aquatic organisms'. The articles explore how natural and anthropogenic factors can constrain these two fundamental activities in a diverse range of organisms from phytoplankton to marine mammals. Some major environmental constraints derive from the intrinsic properties of the fluid and are mechanical in nature, such as viscosity and flow regime. Other constraints derive from direct effects of factors, such as temperature, oxygen content of the water or turbidity, upon the mechanisms underlying the performance of locomotion and predator-prey interactions. The effect of these factors on performance at the tissue and organ level is reflected in constraints upon performance of the whole organism. All these constraints can influence behaviour. Ultimately, they can have an impact on ecological performance. One issue that requires particular attention is how factors such as temperature and oxygen can exert different constraints on the physiology and behaviour of different taxa and the ecological implications of this. Given the multiplicity of constraints, the complexity of their interactions, and the variety of biological levels at which they can act, there is a clear need for integration between the fields of physiology, biomechanics, behaviour, ecology, biological modelling and evolution in both laboratory and field studies. For studies on animals in their natural environment, further technological advances are required to allow investigation of how the prevailing physico-chemical conditions influence basic physiological processes and behaviour.     

The power of statistical tests using field trial count data of nontarget organisms in environmental risk assessment of genetically modified plants

相似文献   

Risk assessment and ecological effects of transgenic Bacillus thuringiensis crops on non-target organisms

The application of recombinant DNA technology has resulted in many insect-resistant varieties by genetic engineering (GE). Crops expressing Cry toxins derived from Bacillus thuringiensis (Bt) have been planted worldwide, and are an effective tool for pest control. However, one ecological concern regarding the potential effects of insect-resistant GE plants on non-target organisms (NTOs) has been continually debated. In the present study, we briefly summarize the data regarding the development and commercial use of transgenic Bt varieties, elaborate on the procedure and methods for assessing the non-target effects of insect-resistant GE plants, and synthetically analyze the related research results, mostly those published between 2005 and 2010. A mass of laboratory and field studies have shown that the currently available Bt crops have no direct detrimental effects on NTOs due to their narrow spectrum of activity, and Bt crops are increasing the abundance of some beneficial insects and improving the natural control of specific pests. The use of Bt crops, such as Bt maize and Bt cotton, results in significant reductions of insecticide application and clear benefits on the environment and farmer health. Consequently, Bt crops can be a useful component of integrated pest management systems to protect the crop from targeted pests.     

积雪变化对陆地生态系统植被特征和土壤碳氮过程的影响

在季节性积雪地区,冬季气候变暖导致积雪变薄、积雪不连续、融雪提前及雪盖面积缩小等现象。然而相较于氮沉降、增温、降水变化等全球变化因子,目前尚缺乏积雪因子对陆地生态系统过程和功能影响的系统报道。为加深人们对积雪特征变化生态后果的认知,综述了积雪深度和融雪时间变化对植被物候和群落组成、凋落物分解、土壤碳氮过程、温室气体排放和土壤微食物网(土壤动物和微生物)的影响。由于模拟积雪变化手段不同和复杂的气候、土壤背景,生态系统各要素对积雪特征变化的响应规律存在较大的分异和不确定性。例如,在未来气候变暖导致积雪变薄和融雪提前情景下,植被物候提前,生长季延长,导致生产力增加和凋落物数量增加,禾草比例减少导致凋落物质量增加,早春温度高刺激微生物活性,凋落物分解速率高,促进土壤碳氮周转过程。但积雪减少和融雪提前导致的早春低温和夏季干旱也可能引起植被生产力下降,凋落物数量减少质量降低,土壤微生物活性低,分解速率低,从而减缓碳氮周转过程。此外,积雪特征变化对植被特征和土壤碳氮过程影响相关研究目前还存在以下问题：1)积雪深度和融雪时间对生态系统的影响是否存在交互效应仍缺乏关注,且积雪变化对后续生长季是否存在持续...     

First record of preserved soft parts in a Palaeozoic podocopid (Metacopina) ostracod, Cytherellina submagna: phylogenetic implications

The metacopines represent one of the oldest and most important extinct groups of ostracods, with a fossil record from the Mid-Ordovician to the Early Jurassic. Herein, we report the discovery of a representative of the group with three-dimensionally preserved soft parts. The specimen--a male of Cytherellina submagna--was found in the Early Devonian (416 Ma) of Podolia, Ukraine. A branchial plate (Bp) of the cephalic maxillula (Mx), a pair of thoracic appendages (walking legs), a presumed furca (Fu) and a copulatory organ are preserved. The material also includes phosphatized steinkerns with exceptionally preserved marginal pore canals and muscle scars. The morphology of the preserved limbs and valves of C. submagna suggests its relationship with extant Podocopida, particularly with the superfamilies Darwinuloidea and Sigillioidea, which have many similar characteristic features, including a large Bp on the Mx, the morphology of walking legs, Fu with two terminal claws, internal stop-teeth in the left valve, adductor muscle scar pattern, and a very narrow fused zone along the anterior and posterior margins. More precise determination of affinities will depend on the soft-part morphology of the cephalic segment, which has not been revealed in the present material.     

Local sex-ratio dynamics: a model for the dioecious liverwort Marchantia inflexa

In many dioecious bryophyte species, population sex ratios range from all female to all male. The focal species of the present study, the liverwort Marchantia inflexa, forms patches on rock and bark surfaces, and these differ widely in sex ratio at a rainforest field site in Trinidad. This analysis – to our knowledge the first modeling study of sex-ratio dynamics in a dioecious clonal organism – addresses abundances of male and female M. inflexa through time within an individual patch. We represent the life history of this species using seven different stages (non-reproductive, asexually reproductive, sexually reproductive males, non-reproductive, asexually reproductive, unfertilized and fertilized sexual females) and express their dynamics using ordinary differential equations. Some of the stages become more abundant as thalli extend over the substrate and may overgrow each other to capture space. Our simple representation of dynamics within the patch failed to stabilize the sex ratio: females gradually eliminated males at low to moderate disturbance frequency and males eliminated females at high disturbance frequency. This pattern did not hinge on whether sexual propagules could germinate within the patch, but asexual reproduction (via gemmae dispersed within the patch) played an important role. This suggests that the maintenance of sex in these populations may hinge on metapopulation structure and dynamics. Though sexual reproduction appears to be unimportant within patches, spores provide the primary means of recolonizing patches eliminated by large-scale disturbances. We found that shortly after the patch was fully occupied, the production of these wind-dispersed spores was maximized, but spore production declined thereafter as the sex ratio became increasingly biased toward one sex or the other. Much additional modeling and empirical work is needed to link within-patch dynamics across patches and account for dynamics at the metapopulation level.     

Monstrous Tetrahymena with Intraclonal Variation in Structure Produced by Hereditary Modification of Normal Cells

SYNOPSIS Monstrous Tetrahymena pyriformis strain GL may be isolated after exposure of normal cells to numerous heat shocks, to flattening on agar or gelatin plates, or to viscous solutions of methyl cellulose. It is shown that in some cases the abnormalities are inherited and that this results in clones where the cells are different from each other and have various abnormalities with respect to cortical pattern, swimming and feeding behavior, and generation time. Furthermore, it is shown that these cells are produced rather than selected by the experimental treatments. Evidence is presented that growth without division is important for production of the abnormal organisms. The basis of the inheritance of the abnormalities is discussed.